[NET]: Rework dev_base via list_head (v3)

Cleanup of dev_base list use, with the aim to simplify making device
list per-namespace. In almost every occasion, use of dev_base variable
and dev->next pointer could be easily replaced by for_each_netdev
loop. A few most complicated places were converted to using
first_netdev()/next_netdev().

Signed-off-by: Pavel Emelianov <xemul@openvz.org>
Acked-by: Kirill Korotaev <dev@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 45 insertions, 51 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index c305819b726..f27d4ab181e 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -156,13 +156,13 @@ static spinlock_t net_dma_event_lock;
 #endif
 
 /*
- * The @dev_base list is protected by @dev_base_lock and the rtnl
+ * The @dev_base_head list is protected by @dev_base_lock and the rtnl
  * semaphore.
  *
  * Pure readers hold dev_base_lock for reading.
  *
  * Writers must hold the rtnl semaphore while they loop through the
- * dev_base list, and hold dev_base_lock for writing when they do the
+ * dev_base_head list, and hold dev_base_lock for writing when they do the
  * actual updates.  This allows pure readers to access the list even
  * while a writer is preparing to update it.
  *
@@ -174,11 +174,10 @@ static spinlock_t net_dma_event_lock;
  * unregister_netdevice(), which must be called with the rtnl
  * semaphore held.
  */
-struct net_device *dev_base;
-static struct net_device **dev_tail = &dev_base;
+LIST_HEAD(dev_base_head);
 DEFINE_RWLOCK(dev_base_lock);
 
-EXPORT_SYMBOL(dev_base);
+EXPORT_SYMBOL(dev_base_head);
 EXPORT_SYMBOL(dev_base_lock);
 
 #define NETDEV_HASHBITS	8
@@ -567,11 +566,12 @@ struct net_device *dev_getbyhwaddr(unsigned short type, char *ha)
 
 	ASSERT_RTNL();
 
-	for (dev = dev_base; dev; dev = dev->next)
+	for_each_netdev(dev)
 		if (dev->type == type &&
 		    !memcmp(dev->dev_addr, ha, dev->addr_len))
-			break;
-	return dev;
+			return dev;
+
+	return NULL;
 }
 
 EXPORT_SYMBOL(dev_getbyhwaddr);
@@ -581,11 +581,11 @@ struct net_device *__dev_getfirstbyhwtype(unsigned short type)
 	struct net_device *dev;
 
 	ASSERT_RTNL();
-	for (dev = dev_base; dev; dev = dev->next) {
+	for_each_netdev(dev)
 		if (dev->type == type)
-			break;
-	}
-	return dev;
+			return dev;
+
+	return NULL;
 }
 
 EXPORT_SYMBOL(__dev_getfirstbyhwtype);
@@ -617,17 +617,19 @@ EXPORT_SYMBOL(dev_getfirstbyhwtype);
 
 struct net_device * dev_get_by_flags(unsigned short if_flags, unsigned short mask)
 {
-	struct net_device *dev;
+	struct net_device *dev, *ret;
 
+	ret = NULL;
 	read_lock(&dev_base_lock);
-	for (dev = dev_base; dev != NULL; dev = dev->next) {
+	for_each_netdev(dev) {
 		if (((dev->flags ^ if_flags) & mask) == 0) {
 			dev_hold(dev);
+			ret = dev;
 			break;
 		}
 	}
 	read_unlock(&dev_base_lock);
-	return dev;
+	return ret;
 }
 
 /**
@@ -693,7 +695,7 @@ int dev_alloc_name(struct net_device *dev, const char *name)
 		if (!inuse)
 			return -ENOMEM;
 
-		for (d = dev_base; d; d = d->next) {
+		for_each_netdev(d) {
 			if (!sscanf(d->name, name, &i))
 				continue;
 			if (i < 0 || i >= max_netdevices)
@@ -975,7 +977,7 @@ int register_netdevice_notifier(struct notifier_block *nb)
 	rtnl_lock();
 	err = raw_notifier_chain_register(&netdev_chain, nb);
 	if (!err) {
-		for (dev = dev_base; dev; dev = dev->next) {
+		for_each_netdev(dev) {
 			nb->notifier_call(nb, NETDEV_REGISTER, dev);
 
 			if (dev->flags & IFF_UP)
@@ -2049,7 +2051,7 @@ static int dev_ifconf(char __user *arg)
 	 */
 
 	total = 0;
-	for (dev = dev_base; dev; dev = dev->next) {
+	for_each_netdev(dev) {
 		for (i = 0; i < NPROTO; i++) {
 			if (gifconf_list[i]) {
 				int done;
@@ -2081,26 +2083,28 @@ static int dev_ifconf(char __user *arg)
  *	This is invoked by the /proc filesystem handler to display a device
  *	in detail.
  */
-static struct net_device *dev_get_idx(loff_t pos)
+void *dev_seq_start(struct seq_file *seq, loff_t *pos)
 {
+	loff_t off;
 	struct net_device *dev;
-	loff_t i;
 
-	for (i = 0, dev = dev_base; dev && i < pos; ++i, dev = dev->next);
+	read_lock(&dev_base_lock);
+	if (!*pos)
+		return SEQ_START_TOKEN;
 
-	return i == pos ? dev : NULL;
-}
+	off = 1;
+	for_each_netdev(dev)
+		if (off++ == *pos)
+			return dev;
 
-void *dev_seq_start(struct seq_file *seq, loff_t *pos)
-{
-	read_lock(&dev_base_lock);
-	return *pos ? dev_get_idx(*pos - 1) : SEQ_START_TOKEN;
+	return NULL;
 }
 
 void *dev_seq_next(struct seq_file *seq, void *v, loff_t *pos)
 {
 	++*pos;
-	return v == SEQ_START_TOKEN ? dev_base : ((struct net_device *)v)->next;
+	return v == SEQ_START_TOKEN ?
+		first_net_device() : next_net_device((struct net_device *)v);
 }
 
 void dev_seq_stop(struct seq_file *seq, void *v)
@@ -3082,11 +3086,9 @@ int register_netdevice(struct net_device *dev)
 
 	set_bit(__LINK_STATE_PRESENT, &dev->state);
 
-	dev->next = NULL;
 	dev_init_scheduler(dev);
 	write_lock_bh(&dev_base_lock);
-	*dev_tail = dev;
-	dev_tail = &dev->next;
+	list_add_tail(&dev->dev_list, &dev_base_head);
 	hlist_add_head(&dev->name_hlist, head);
 	hlist_add_head(&dev->index_hlist, dev_index_hash(dev->ifindex));
 	dev_hold(dev);
@@ -3360,8 +3362,6 @@ void synchronize_net(void)
 
 void unregister_netdevice(struct net_device *dev)
 {
-	struct net_device *d, **dp;
-
 	BUG_ON(dev_boot_phase);
 	ASSERT_RTNL();
 
@@ -3381,19 +3381,11 @@ void unregister_netdevice(struct net_device *dev)
 		dev_close(dev);
 
 	/* And unlink it from device chain. */
-	for (dp = &dev_base; (d = *dp) != NULL; dp = &d->next) {
-		if (d == dev) {
-			write_lock_bh(&dev_base_lock);
-			hlist_del(&dev->name_hlist);
-			hlist_del(&dev->index_hlist);
-			if (dev_tail == &dev->next)
-				dev_tail = dp;
-			*dp = d->next;
-			write_unlock_bh(&dev_base_lock);
-			break;
-		}
-	}
-	BUG_ON(!d);
+	write_lock_bh(&dev_base_lock);
+	list_del(&dev->dev_list);
+	hlist_del(&dev->name_hlist);
+	hlist_del(&dev->index_hlist);
+	write_unlock_bh(&dev_base_lock);
 
 	dev->reg_state = NETREG_UNREGISTERING;
 
diff --git a/net/core/dev_mcast.c b/net/core/dev_mcast.c
index 7d57bf77f3a..5a54053386c 100644
--- a/net/core/dev_mcast.c
+++ b/net/core/dev_mcast.c
@@ -223,7 +223,7 @@ static void *dev_mc_seq_start(struct seq_file *seq, loff_t *pos)
 	loff_t off = 0;
 
 	read_lock(&dev_base_lock);
-	for (dev = dev_base; dev; dev = dev->next) {
+	for_each_netdev(dev) {
 		if (off++ == *pos)
 			return dev;
 	}
@@ -232,9 +232,8 @@ static void *dev_mc_seq_start(struct seq_file *seq, loff_t *pos)
 
 static void *dev_mc_seq_next(struct seq_file *seq, void *v, loff_t *pos)
 {
-	struct net_device *dev = v;
 	++*pos;
-	return dev->next;
+	return next_net_device((struct net_device *)v);
 }
 
 static void dev_mc_seq_stop(struct seq_file *seq, void *v)
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index cec11110915..8c971a2efe2 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -539,13 +539,16 @@ static int rtnl_dump_ifinfo(struct sk_buff *skb, struct netlink_callback *cb)
 	int s_idx = cb->args[0];
 	struct net_device *dev;
 
-	for (dev=dev_base, idx=0; dev; dev = dev->next, idx++) {
+	idx = 0;
+	for_each_netdev(dev) {
 		if (idx < s_idx)
-			continue;
+			goto cont;
 		if (rtnl_fill_ifinfo(skb, dev, NULL, 0, RTM_NEWLINK,
 				     NETLINK_CB(cb->skb).pid,
 				     cb->nlh->nlmsg_seq, 0, NLM_F_MULTI) <= 0)
 			break;
+cont:
+		idx++;
 	}
 	cb->args[0] = idx;